1. Field of the Invention
The present invention relates to long life instrumentation magnetic transducers and, more particularly, to a method of manufacturing an instrumentation magnetic transducer so as to substantially extend the operating life thereof.
2. Description of the Prior Art
One of the singular most important parts of a magnetic tape recording and playback system is the transducer which converts electrical signals to magnetic signals and back to electrical signals. While the magnetic transducer was often a highly limiting factor in wideband instrumentation recorder/reproducers, this technology has, throughout the years, improved tremendously. As a consequence, today's high performance magnetic tape recorders can be equipped with transducers that exhibit longer life, higher frequency response, and better signal-to-noise ratios. New modern equipment, combined with years of practical experience, has enabled head manufacturing firms to produce products that are quite superior, both electrically and mechanically, to those available a few short years ago.
For example, about a decade ago, 14 signal tracks was the maximum number allowed for one-inch magnetic tape. As to frequency response, 100 kHz was about the maximum at a tape speed of 60 inches per second (ips). Today, one can obtain 42 signal tracks on one-inch wide tape with a bandwidth of up to 2 MHz at 120 ips. During the 1980's, the recorder/reproducer user will, without a doubt, be offered extended bandwidth capabilities; i.e. three to four Mhz at 120 ips.
There are a number of different types of magnetic transducers that have been developed for wideband magnetic tape recording. One highly desirable type will be referred to herein as the hard-tipped magnetic head and this type of magnetic transducer is described in U.S. Pat. Nos. 3,614,339 and 3,663,765. A hard-tipped magnetic transducer is assembled in two half-bracket pieces which are bolted and/or epoxied together prior to final contouring of the head surface. These half brackets are slotted for receipt of ferrite cores which are wound with the proper number of turns and size of wire. The cores in each half bracket have edge faces which all lie substantially in a common plane which is common with a first surface of each of the brackets. A pair of tip plates are slotted to accomodate shields and grooved in the bottom surfaces thereof for receipt of pole tips made from a very hard, wear resistant material. The tip plates containing the pole tips are then secured to the half brackets having the cores therein, with the bottom surfaces of the tip plates secured to the respective first surfaces of the half brackets. The pole tips engage the edge faces of the cores with a coupling gap between the pole tips so as to define a plurality of signal channels. When viewing the tip plates from the top surfaces thereof after they are attached to the half brackets, the pole tips cannot initially be seen.
Laminated shields are then inserted into the slotted half brackets and the matching half brackets are bonded together. Various epoxies and a minimum of two bolts are used to assure a lasting bond. After the half brackets are attached to form a head stack, contouring and lapping of the top surfaces of the tip plates is performed. This exposes the pole tips and their magnetic circuits to the magnetic tape path.
The surface of the head which is exposed to the magnetic tape includes the pole tips, the laminated shields, and the body of the tip plates between these two elements. Because of the friction generated by the tape moving across this surface, wear to the various elements results. Since the pole tips are made from an extremely hard material, they tend to wear relatively slowly. On the other hand, between the active signal channels of the head, the surfaces of the tip plates provide an area of relatively softer material which typically wears at a faster rate. Since this area wears faster, track edge rounding occurs which ultimately results in head failure due to wear.
Several approaches have been suggested for the solution of this problem. One approach has been the addition of low wear materials to the surface of the heads between the active channels. This has alleviated the problem somewhat, but not in a significant manner. Other solutions include an entirely different head design including ferrite and ceramic materials for the tip plates. These are very expensive solutions and solutions which are often electrically undesirable because of noise problems. In other words, the solutions proposed heretofore have come with their own disadvantages, which have often been equally or more undesirable. If a hard wearing surface could be provided between the active channels without excessive cost and without undesirable electrical characteristics, head life could be extended. However, this has been unachievable heretofore.